1. Field of the Invention
The present invention relates generally to a composite terminal, and more particularly to a method for accessing a Subscriber Identification Module (SIM) in a composite terminal.
2. Description of the Related Art
Recently, cell phones have developed to provide users with various supplementary functions in addition to a simple telephone, to the point where cell phones have become necessities. In particular, to provide both personal information management function and telephone function, a composite terminal—a combination cell phone and Personal Digital Assistant (PDA)—has been developed to provide convenient use of the personal information management function by means of a portable cell phone.
FIG. 1 is a block diagram of a typical composite terminal. Referring to FIG. 1, a phone module 2 performs cell phone functions including a call originating operation and a call terminating operation. A PDA module 4 performs PDA functions including a schedule management function, a memo function and a management function of various data. A phone/PDA interface unit 6 is connected between the phone module 2 and the PDA module 4 to perform data communication between the two modules. A SIM 8 stores secret identification data for a cell phone service provider, subscriber identification information such as subscriber information, and user data such as a phone book and Short Message Service (SMS) data.
Typically, the SIM 8 as described above is shaped like a small card and installed in the phone module 2. Further, the SIM 8 is constructed so as to be accessible exclusively by the phone module 2 to access the secret identification data, subscriber identification information, or user data stored in the SIM 8.
However, since the PDA module 4 cannot access the SIM 8, the PDA module 4 receives the subscriber identification information and the user data through the phone module 2.
Accordingly, the method described above is extremely time-consuming since the PDA module 4 cannot directly read the requested information. Additionally, if other information is to be received from the phone module 2 occurs while the PDA module 4 receives the subscriber identification information, the PDA module 4 receives both information at the same time. The probability of an error increases from a collision of the two flows of information.
The present invention prevents such a data collision, by restricting transmission of other information during reception of the subscriber identification information or the user data, and by stopping the PDA module 4 from using functions relating to the phone module 2 during the restricted time period.